U.S. Pat. No. 2,418,000 discloses the preparation of MBH from hydantoin and a formaldehyde source including paraformaldehyde, anhydrous formaldehyde gas or 37% formaldehyde solution in the presence of HCl and water, wherein the concentration of water is between 13-30 weight percent of the reaction mixture. The preferred concentration of water is between 18-27 weight percent. The specification of U.S. Pat. No. 2,418,000 specifically states that if the water content of the reaction mixture is greater than 30 weight percent, the desired product is produced in very low yields. Although the preferred embodiment of that procedure is reported to give MBH in 87% yield, the amount of solvent used is so small, and MBH is so insoluble that the reaction mixture solidifies upon completion of the reaction. A solidified product in the reaction vessel is undesirable because of the increased handling procedures required to remove and/or transfer the product.
Due to the importance of N-(phosphonomethyl)glycine, new and alternative methods of preparation of this beneficial herbicide are continually being explored. In addition, newly improved methods of preparation are also desirable.
It is an object of the present invention to provide an improved method for the preparation of MBH. It is a further object of this invention to reduce the cost of producing PMG by increasing the reaction yield of MBH. A still further object of this invention is to include in the reaction medium a sufficient amount of water to produce a stirrable reaction mixture, thereby increasing ease of product handling